Formation of the eye begins during the initial stages of vertebrate embryogenesis, a period when many inherited or environmentally determined malformations affecting the eye have their origin. Our long term goal, a basic understanding of this developmental process is likely to provide considerable insight into the diagnosis, prevention and treatment of such disorders. Crucial to our understanding of this process is knowing the identity of genes selectively expressed in the cellular primordia which define the early eye. Such genes are strong candidates for the genes which govern eye morphology and the determination of its cell types. Human counterparts of these genes are also prime candidates for genes defective in inherited eye disorders. Less severe malfunctions of such genes are also of interest as possible risk factors contributing to more common diseases such as cataract and glaucoma. Currently, very few genes are known that are selectively expressed in the early optic vesicle and lens primordium. The optic vesicle, an outgrowth of the embryonic forebrain, gives rise to the optic nerve, retina, pigment epithelium, ciliary body and iris. The lens primordium region of the undifferentiated head ectoderm generates the lens as well as the corneal epithelium. Currently, the only known gene selectively expressed in these primordia is Pax-6, a transcriptional regulator essential to early development of the eye. Defects in one copy of the human Pax-6 gene cause aniridia, an inherited ocular malformation syndrome. The scope of this proposal is to isolate novel genes selectively expressed in the optic vesicle and lens primordium of the chick embryo. This will be accomplished by the micro-dissection of optic vesicles and lens primordia followed by the use of new techniques to generate cDNA libraries which represent the mRNA populations extracted from these small samples of tissue. Differential screening will identify genes expressed at higher levels in these early eye primordia, and further screening by in situ hybridization of whole embryos will be used to determine their detailed pattern of expression. For genes exhibiting distinctive expression patterns involving elements of the early eye, full length cDNA clones will be isolated and their sequence determined. This sequence information will provide clues to the cellular localization and function of the encoded protein, as will the preparation of antibodies specific for these proteins. Finally, homologous human genes will be isolated and then mapped to individual human chromosomes in order to provide a starting point for the identification of clinical disorders which might be associated with these genes.